NY

We have quite the complicated winter storm on our hands for tonight through tomorrow, with some snow/mixed precipitation expected on the leading edge of the system that will change over to rain in many areas before the back edge transitions over to snow. Accumulations of 1″+ are mostly reserved for the mountains where the back-end snow will last long enough for such accumulations, with the westernmost areas expected to be all snow. Snow and mixed precipitation at the start of the event tomorrow morning is difficult to assess in both the start time and duration before it changes over to rain, and will generally be west of (and maybe a little east of) I-95. Isentropic lift will battle against dry air in the lower levels at the onset early tomorrow morning, with steadier precipitation moving in between mid-morning and mid-afternoon across most of the region.

If temperatures are cooler at the onset of precipitation, snowfall may be able to get to 1″ east of the forecast line before changing over to rain. Widespread rainfall of 1-3″+ is expected along/east of the Appalachians as this system moves through tomorrow afternoon through Wednesday before the back edge switches over to snow. The wet, saturated ground could hurt snow totals on the back edge of this system unless the snowfall rates are good enough to overcome this obstacle.

Made some changes to bring things a bit further east in general. I took out the 4-8 inch contour due to uncertainties in the forecast, but I do think there will be localized 4-8″ totals in eastern PA and western NJ. Confidence in the forecast is normal to slightly below normal.

Here we go with another early start to winter… but early start for who, exactly?

Well, the mountains already got a shock to the system last week as Sandy dumped as much as three feet or more of snow across West Virginia. This time around, it looks like the coastal areas will cash in more as those out west are left to deal with whatever remains of what they got last week. The latest model runs have (thankfully) converged on a somewhat reasonable solution for mid-week’s snow.

Despite the recent convergence, forecast confidence is still lower than normal as small shifts in the storm track could potentially lead to big shifts in the snow zone.

This storm is going to be mostly an Appalachian event, with heavy, wet snow creating problems with falling branches and trees and power outages in the areas forecast to get 2-4 inches of snow or more.

The bulk of the snow will fall on Monday as the coastal low deepens and works into eastern PA and central NY. Areas east of the one inch line could see some minor snow accumulation as the rain changes over to snow during the tail end of the event. Snow totals in northeastern OH, western PA and western NY will get a boost from lake enhancement. Locally higher totals are possible in the highest elevations.

A strong coastal storm will develop tomorrow into Monday, and this low will actually retrograde inland, eventually making its way into central NY.

This late season storm is expected to bring 6-12 inches or more to the higher elevations of the central Appalachians, with lower totals in the lower elevations as the snow battles against boundary layer temperature issues and warmer ground. Of course, higher snowfall rates could overcome these problems fairly quickly, so we’ll have to keep an eye on places like western PA and western NY as the storm develops to see just how much those areas might get.

The NWS is putting up Winter Storm Watches in the higher elevations and in some of the higher-impact low elevation areas for when the storm moves through late Sunday into Monday. Along the coast, widespread rain totals of 1-3 inches are in the forecast, which will help alleviate some of the drought conditions that have developed over the last several months.

A lot of locales in the Northeast are experiencing their first sub-zero lows of the winter, with temperatures as cold as -24F in Watertown, NY! (Yes, it’s -24, not -23. The software rounds the Celsius conversions oddly in some cases)

A 1030mb high centered over southeastern Ontario is allowing for light to calm winds under mostly clear skies.

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UPDATE: Grabbed the hour with the coldest temperatures and updated the map.

Not going to put a map out on this one, but the first significant lake-effect snow storm of the season is nearly upon us. Locally, the mountains of West Virginia could see 6-12″ with localized amounts of 12-18″+ in the best-positioned areas. Similar totals can also be expected downwind of Lake Ontario and Lake Erie (though Ontario more so).

The story is starting to make itself known as the high-resolution models can start picking up on event QPF totals for the region:

Now, not all of that QPF is for snow… you will have to cut out about 0.25″-0.50″ of that for the highest elevations as they get hit by rain before the changeover. Even after that, you’re looking at a solid 0.5″-1.0″ of QPF for a lake-effect event that will likely be producing snowfall ratios of 15-25:1, yielding low-end ranges of 8-16″ and higher-end ranges of 12-24″ in the QPF bulls-eyes. Widespread 5-10″+ along the hilltops of West Virginia seems like a pretty solid forecast at this point.

However, if you are REALLY looking for a good lake-effect event, head up to the Tug Hill Plateau east of Lake Ontario. Look at the map above again… you’ll see what I’m talking about. If you don’t, the NWS certainly does:

* IMPACTS…THE COMBINATION OF LOCALLY HEAVY LAKE EFFECT SNOW AND
STRONG GUSTY WINDS WILL RESULT IN PERIODS OF WHITEOUT CONDITIONS
WHICH WILL MAKE TRAVEL VERY DIFFICULT OR EVEN NEARLY IMPOSSIBLE
AT TIMES WITH LOCALIZED BLIZZARD CONDITIONS. TRAVEL ALONG
INTERSTATE 81 AND ADJACENT ROADWAYS WILL BE SEVERELY IMPACTED
BY THE INCLEMENT WEATHER CONDITIONS.

There will quite possibly be enough moisture around after the lake-effect impacts the mountains to get flurries and maybe a stronger burst or two of snow east of the mountains… but don’t expect more than a dusting (unless you can get really, really lucky).